EP1147730A1 - Espresso type coffee machine with two thermostats - Google Patents

Abstract

The coffee maker has a cold water reservoir (1), a pump (2) and a heating unit (3) having a first and second thermostat (33,34), and a filter (6). The second thermostat (34) whose temperature limit is high, is put in service at the same time as the pump to produce hot water necessary for making coffee.

Description

The present invention relates to pressure coffee makers of the espresso type.

This type of coffee maker most often has a production function of steam, which is used to heat a drink. To do this hot water generator can be set to a temperature higher than that of boiling water.

We know for example from patent FR2465451 coffee makers equipped two thermostats that allow the coffee maker boiler to heat up water at two different temperatures, depending on the desired use, i.e. as infusion liquid or as superheated steam.

The water enters the heating body of the coffee maker and heats up in the process. The temperature of the heating body is adjusted to obtain good coffee temperature in the receiving cup. However, the first introduction of water in the heater actually lowers the temperature significantly before the thermostat could not respond, so successive cup coffees have insufficient or irregular temperatures.

When the water becomes insufficiently hot we could stop the pump as suggested in patent US4109565, but this process is obviously wrong felt by the impatient user or who can think of a breakdown.

We know coffee makers for example by patent FR2774882 where this problem is solved by an electronic control circuit, much more reactive than a simple thermostat generally with bimetallic strip. However such an order electronic specific to the coffee maker increases the cost price.

The object of the invention below is an economical coffee maker not having the disadvantages mentioned above.

The object of the invention is achieved by a coffee maker having a reservoir of cold water, a pump, a heating block equipped with a first and a second thermostat, a filter, remarkable in that the second thermostat including the setpoint is higher is put into service at the same time as the pump for produce the hot water necessary for coffee.

The invention is fully satisfied with set electromechanical thermostats inexpensive fixed. However we can find advantage to use two thermostats simple electronic for special reasons, of size or implementation for example, without departing from the scope of the invention. Can also use a single sensor of a simple electronic thermostat whose signal is compared to one of two fixed setpoint values, one corresponding to the set temperature of the first thermostat, the other to that of the second thermostat without departing from the scope of the invention. In what follows we will assume, for for clarity, the coffee maker is equipped with two thermostats.

In this way, the heating block is adjusted by a first thermostat to a first temperature for example 95 ° C sufficient to bring the water to the temperature required for coffee extraction. When starting the pump, a second thermostat with a higher set temperature for example 115 ° C is put into service. The difference between this temperature of setpoint and the block temperature at start-up is added to the drop in temperature of the heating block due to the passage of water. This gives a signal strong thermostat which quickly supplies electrical power of heating.

Preferably the installed power of the coffee maker is suitable for heating the nominal flow of water for coffee at extraction temperature.

We know that it takes about 335 Joules to heat a cubic centimeter of water the temperature of withdrawal or storage in the tank (about 15 ° C) at the coffee extraction temperature (around 95 ° C),

But in all cases the thermal inertia of the heating block contributes to smoothing differences in water temperature that could occur due to difference in adaptation between the heating power and the water flow. If the installed power is properly adjusted, we can even consider reduce the mass of the heating block, the thermal inertia no longer being essential. The water is thus at the right temperature for the entire duration of percolation.

When the user stops the pump, the first thermostat resumes control of the temperature of the heating block, so that when the water flow stops it does not no overheating occurs, and the coffee maker is immediately available for a new percolation.

Preferably the coffee maker has a steam production function during which, when used, the second thermostat controls the temperature of the heating block.

The same second thermostat is used to control the heating block during percolation and to obtain steam. During percolation the heating power and heat exchange conditions are insufficient opposite the water flow so that the water temperature rises to the temperature setpoint, while during steam production, the water flow from the pump is reduced so that the heating block remains at a temperature sufficient to obtain good vaporization.

This reduction in water flow can conventionally be obtained by throttling of the steam outlet, or by a throttling of the circuit water, or by reducing the pump flow by electrical means, or by any other combination of known means.

Reducing water flow is a simple and satisfactory solution, but any solution to obtain a sufficient ratio between electrical power and the power required to evaporate the water flow allows the application of the invention. We can thus increase the power supplied during vaporization for example by supplying a second heating element to the heating body, by reducing the water flow less to obtain a greater steam flow.

The invention will be better understood on the basis of the example below and of the drawings attached.

Figure 1 is a side view of a coffee maker according to the invention, in section partial of the envelope, the tank and the heating body.

Figure 2 is a front view of the control button.

Figure 3 is a block electrical diagram of the invention.

FIG. 4 is a temperature diagram of the heating block as a function of the time before and during the extraction of a coffee.

FIG. 5 is a temperature diagram of the heating block as a function of the time before and during steam production.

In a preferred embodiment the coffee maker has a water circuit consisting from upstream to downstream by a water tank 1, an electromagnetic pump 2, a heating body 3, a distributor 4, a support 5 and a filter holder 6 containing the ground coffee. The coffee is received in a receptacle 7 which can be a cup. The coffee maker further comprises a steam duct 9 supplied by the distributor 4 and terminated by a nozzle 10 comprising a calibrated nozzle, this under together being accessible by the user,

The user has a command 11 acting simultaneously on the distributor 4 and on an electrical switch 12.

The heating block 3 is an aluminum block comprising channels 31 in which the water from pump 2 heats up and eventually turns into steam. The electric heating element 32 supplies the energy necessary for this block, which is equipped with a first thermostat electromechanical 33 set in the vicinity of 105 ° C (t1 ° in Figures 4 and 5) and a second electromechanical thermostat 34 set to around 125 ° C (t2 ° on the Figures 4 and 5).

The distributor 4 is capable of establishing the hydraulic connection between the block heater 3 and filter 6 to make coffee or between heater 3 and outlet of steam 9-10 when you want to heat a drink. This distributor is controlled by the user at the same time as the switch 12 by the button 11 which can take five positions marked P0 to P4 on the figures 3-5 and by pictograms visible in figure 2 under the button control 11. The control button 11 simultaneously drives sliding contacts 41 and 42 of the switch 12 so that in FIG. 3 the contacts 41, 42 align with one of the positions P0 to P4, the center lines of which are mixed line correspond to the pictograms in figure 2.

Position 0 of the control button and P0 of the switch is the position the coffee maker. The electric current of the sector arrives by the identified wires L1 and L2 but no element is supplied.

When the user wants to prepare coffee, he acts at a time t1 on the control to heat the coffee maker in position P1 of the switch. AT the electric current can flow from L1 to the heating element 32 being controlled by the first thermostat 33 set to the necessary temperature to get a coffee.

Usefully a heating indicator 35 in parallel with the heating element 32 lights up until the set temperature is reached, then turns off when the first thermostat 33 opens.

The coffee maker thus being ready, the user orders at a time t2 the extraction of the coffee by moving the switch to position P2. Distributor 4 then connects the heating block 3 to the filter holder 6. The electric current flows from L1 to the pump 2 and via the thermostat 34 to the heating element 32 and its indicator light heats 35. The temperature of the heating block 3 being lower than the temperature setpoint t2 ° of thermostat 34, the heating is switched on. The power of the heating element 32 is substantially adjusted by construction to the power consumed by heating water. The water circulating by heating in the heating block 3 keeps the temperature substantially constant as is see it in solid line on the diagram of figure 4. Power differences absorbed due to variations in water flow due to settlements other than the grind for example are low compared to the total power consumed and are absorbed by the thermal inertia of the heating block. This is all the more true that the coffee extraction time is never very long and that even significant deviations do not have time to manifest themselves. By these means we obtains a good extraction temperature and immediately brings the energy required for coffee throughout the extraction, without causing overheated.

Without the use of a second thermostat with a set temperature t2 ° higher, the first thermostat 33 would not have had time to react from continuation and the temperature of the heating block would have dropped as we can see it shown in dotted lines in Figure 4. Much of the coffee would have then was extracted at too low a temperature and would have produced an unpleasant coffee too cold.

When the coffee is finished, the user can put the coffee maker back in position P1 waiting to extract a new coffee. The pump stops and the coffee maker is again regulated by thermostat 33 to the coffee extraction temperature. he therefore cannot overheat and the coffee maker is ready for new extraction.

The user can also decide to prepare a hot drink. It positions at a time t10 the button 11 so that the switch 12 is in position P3. The heating element 32 is supplied with electrical energy via the thermostat 34 and the heating block 3 heats up to a water vaporization temperature. The setpoint temperature t2 ° of thermostat 34 reached, light 35 goes out.

The user initiates steam production at a time t20 by supplying button 11 the switch in position P4. Pump 2 is supplied with electricity, the heating element 32 continues to be regulated by the thermostat 34. The distributor 4 connects the heating block 3 to the tube 9 which the user immerses the orifice 10 calibrated in the drink to be heated. Water vaporizes on contact with heating block 3 producing a large volume flow of steam. By the way in the calibrated orifice of nozzle 10 the vapor produces an increase of pressure, which decreases the water flow. Hence the power of the element is sufficient to maintain the vaporization temperature, ensuring a jet of continuous steam.

The available power is therefore high compared to that which is consumed. As a result, the temperature of the heating block does not drop much when the vaporization and quickly returns to the set temperature t2 ° as is can see it in figure 5.

In another version the pump 2 includes, or is associated with, a device sequencer causing a decrease in its gait factor, which makes the easier calibration of nozzle opening 10.

In another version the heating element has several resistances and the power is increased during vaporization. The electrical circuit is modified accordingly.

In a simpler version of the coffee maker, which does not have a steam production, positions P3 and P4 of the switch are deleted.

The coffee maker described has the same number of components as a coffee maker classic with a steam production function, but the arrangement of these components allows good regulation of the coffee temperature drink obtained. In a version that does not have a spray function, improvement requires only an additional inexpensive thermostat.

Claims (3)

Coffee maker having a cold water tank (1), a pump (2), a heating block (3) equipped with a first and a second thermostat (33,34), a filter (6), characterized in that the second thermostat (34) whose setpoint is higher is put into operation at the same time as the pump (2) to produce the hot water necessary for the coffee. Coffee maker according to claim 1 characterized in that the installed power of the coffee maker is adapted to heat the nominal flow rate of the water intended for coffee to the extraction temperature. Coffee maker according to one of the preceding claims, characterized in that the coffee maker has a steam production function during which, when it is used, the second thermostat (34) controls the temperature of the heating block (3).

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